Phase I was completed with publication of an NRC contractor report titled: feasibility of coupling a stochastic hourly rainfall generator as input to a deterministic watershed simulation model to develop a synthetic flow record of 1000 years. A stochastic model for the multi-station generation of hourly rainfall was also developed and tested. The overall Phase II effort provides a practical methodology for including severe external flood events into a probabilistic-risk assessment (PRA) study. It can also assist in the assessment of "Safety Margins" for flood protection at nuclear facilities. This work has received favorable review by the National Research Council's Committee on Techniques for Estimating Probabilities for Extreme Floods. Consistent with the SBIR Act, the NRC research contract has the potential for making a significant contribution to the commercial application of the model developed by Linsley, Kraeger Associates. Upon the completion of the software enhancements of the stochastic rainfall generator, and successful testing of the model on the two selected watersheds, the contractor will be able to use the developed methodology for various utilities and DOE contractors. The contractor has also begun inquiries with Electric Power Research Institute to formulate a project to initiate the commercialization effort for use by utilities. The work also has potential benefits for the safety assessments of dams whether or not they are associated with NRC-licensed facilities. 7 The NRC requires nuclear power plant licensees to provide instrumentation in order to detect inadequate core cooling. The licensees, in conformance with this requirement, installed differential pressure cells or heated thermocouple (TC) liquid level probes in their reactor vessels. Both kinds of instruments have some detection limitations. Under Phase I of this contract, Mohr & Associates proposed a liquid level measurement design approach based on time domain reflectometry (TDR) techniques. Under Phase II Mohr & Associates fabricated a model system and demonstrated its capability in the lab. The concept provides industry with an improved alternative for measuring the liquid level in reactor vessels and monitoring core and primary loop water inventory, both of which are needed for safety in reactor operation. Mohr & Associates is now marketing their TDR system. Interest in licensing this system has been expressed by Westinghouse, General Electric and Combustion Engineering. Pfizer Chemical has also expressed interest in using this system to measure the true liquid level in chemical process reactors. 8 Commercial nuclear power plants are large complexes and are comprised of many different systems, components, and structures which cover a broad spectrum of materials and designs. There are a number of factors that can cause degradation of the functional capability of a component, system, or structure. They include material degradation, operating environment, and improper maintenance. These factors, and others, can act with time to degrade a component, system, or structure. Therefore, technical data and regulatory guidance are needed to account for aging degradation in plant safety systems, support systems, and components. Also, improved regulatory guidance is needed to evaluate the effectiveness of inspection, surveillance, and monitoring methods of aging in nuclear power plants. In Phase I, SEA investigated and demonstrated the application of modelling systems interactions to identify components with aging significance. The method involves proper characterication of functional and spatial systems interactions. In Phase II, SEA has applied the systems interaction model procedures, developed in Phase I, to selected safety systems and support systems; identified components and parts which have propensity for aging degradation and generated recommendations for maintenance of the systems to alleviate aging concerns. This research has provided a method to evaluate age and service wear effects from a spatial and functional system interaction perspective. The methodology provides the capability to model the interactions required to complete a plant function (e.g., core cooling) and assess the effect on plant function due to component aging. The output of the research will be used in performing in-depth engineering studies and in developing guidelines for inspection, surveillance and maintenance to alleviate aging concerns. This research demonstrates an application of a practical method for plant operation and aging management. SEA has completed a system operability assurance program for a nuclear generating station under construction. The contractor also developed a procedure to systematically investigate system functional interactions that could effect the safety system design basis. In another case, the contractor is involved with a major utility in demonstrating the potential use of the developed methodology for plant maintenance planning and policy. 9 SUBJECT: GAO Draft Report RCED-89-39, Dated October 31, 1988, TO: Flora H. Milans Associate Director Resources, Community and Economic Development Division The Department of Agriculture does not have any comments on the subject draft report. We appreciate the opportunity to review and comment on the report. Couille Beretty ORVILLE G. BENTLEY |